Wire Stress Research Articles

Use of artificial neural network to assess the effect of mean stress on fatigue of overhead conductors

AbstractThe aim of this work was to use artificial neural networks (ANNs) to model the effect of mean tensile stresses on the fatigue resistance of an aluminum conductor steel reinforced. To train the ANN, fatigue data available for this type of conductor subjected to 2 different levels of mean stresses in the aluminium wires (49 and 74 MPa) were used. It is shown that the use of ANN enabled the construction of constant life diagrams (105, 106, 107, and 108 fatigue loading cycles) for the conductor. These results confirmed that the ANN is able to accurately estimate the effect of mean tensile stresses on conductor durability even considering just a limited number of data for its training.

MEASUREMENTS OF HYSTERESIS LOOPS OF THE MICROWIRES FIXED IN STRETCHED STATE USING THE VIBRATION MAGNETOMETRY

We present a technique of measuring hysteresis loops of the amorphous microwires using a method of vibrating-sample magnetometry. Control magnetic measurements were carried out on samples of an amorphous microwire of Fe 75 B 13 Si 10 C2 composition in a glass shell obtained by the Ulitovsky – Taylor method. The sample was fixed on a specially manufactured experimental setup which enables us to stretch the microwire by means of suspended loads. Fixation of the microwire in the stretched state was carried out by the glue. The stresses in the metal core of the microwire formed upon stretching with suspended loads, as well as the stresses in the contact area of the wire and glue are calculated. The developed method provides fixing of tensile stresses in wires even when the value of stresses may attains a few GPa.

Understanding the compressive behavior of shape memory alloy (SMA)-confined normal- and high-strength concrete

This paper presents the first experimental study on the axial compressive behavior of high-strength concrete (HSC) confined by shape memory alloy (SMA) wire. Concrete cylinders that were prepared using two different grades of concrete, namely normal-strength concrete (NSC) and HSC, were confined with Nitinol (Ni-Ti) SMA spirals having a pitch spacing of 36 and 20 mm, respectively. Preliminary material tests were performed on SMA wires to investigate the tensile strength and strain of SMA in martensitic and austenitic phases and the effect of the temperature on the recovery stress. The confining pressure was applied on concrete cylinders by SMA spirals that were prestrained at 0, 5.5, and 9.5%. The material test results show that an increase in the prestrain level from 5.5% to 9.5% leads to an increase in the recovery stress of SMA wire at temperatures higher than the austenitic finish temperature (90 °C). The compression test results of SMA-confined concrete specimens show that an increase in the prestrain level leads to an increase in the peak axial stress and corresponding axial strain of SMA-confined concrete. Confinement of NSC and HSC specimens by 9.5% prestrained SMA spirals results in a 38.1% and 23.6% higher peak axial stress and a 333% and 346% higher corresponding axial strain, respectively, compared to those of unconfined specimens. It is also shown that because of the more brittle behavior of HSC specimens, SMA-confined HSC fails at a lower axial strain compared to SMA-confined NSC. The lower ultimate axial strain of HSC specimens is also attributed to the lower confinement ratio of the HSC specimens of the current study compared to that of NSC specimens. The promising findings of this study point to the significant potential for the use of SMA spirals in the construction industry for the development of high-performance composite structural members and for strengthening and retrofit of existing concrete members.

Torsional fatigue with axial constant stress of oligo‐crystalline 316L stainless steel thin wire

AbstractA series of symmetric torsional fatigue with axial constant stress tests, a kind of multiaxial fatigue test, was conducted on oligo‐crystalline 316L stainless steel thin wire, which was less than 3.5 grains across diameter of 200 μm. The material presents significant cyclic hardening under symmetric torsion cycling, and hardening is more obvious with the increasing shear strain amplitude. However, symmetric torsional cycle with constant axial stresses tests characterize rapid initial hardening and then gradually softening until fatigue failure. The axial stress has a great effect on torsional fatigue life. Fractography observation shows a mixed failure mode combined torsional fatigue with tensile strain because of axial tensile stress. A newly proposed model with axial stress damage parameter is used to predict the torsional fatigue life with constant axial stress of small scale thin wire.

Modeling of simultaneous shape memory and pseudoelastic effects of shape memory alloys on nonlinear dynamic response of multilayer composite plate embedded with pre-strained SMA wires under thermal condition

ABSTRACTShape memory alloys as a kind of smart materials, have two unique characteristics entitled shape memory and pseudoelastic effects. In this paper, a nonlinear dynamic analysis of multilayered composite plate embedded with pre-strained SMA wires under thermal condition is implemented considering both effects of SMAs simultaneously, for the first time. The constitutive equation proposed by Brinson is used for modelling the behaviors of SMA wires. In this work, equations of motion are derived in the framework of Carrera's Unified Formulation, for robust analysis of the problem. In this regard, the nonlinear strains are employed for modelling the thermal effects and also the effect of recovery stresses in the SMA wires. In this study not only the material properties are instantaneous variable with respect to the time and location, but they are also unknown, which make the problem more complicated. For this aim, a transient nonlinear finite element in conjunction with incremental iterative algorithm proposed by the author is employed, in order to solve the equations. Results show that upon the thermal condition, the recovery stress is generated in the SMA wires and therefore reduce the amplitude of a damped response of the plate. One conclusion from this study is that, in contrast with many studies reported before, it cannot be always say that the stress recovery in SMA wires is increased with increasing the pre-strain of SMA wires. In other words, for a specified increasing in temperature, only a limit amount of pre-strain comes back to its original shape and not more. Also, several numerical examples upon effect of different thermal condition, different volume fraction of SMA wires and different boundary conditions have been analyzed.

Оценка несущей способности канатов заливочных кранов на основании данных лабораторных термических испытаний

The article presents an approach to assessing the bearing capacity of the steel ropes of hot metal cranes used at metallurgical enterprises. The rope bearing capacity is assessed based on the data of laboratory thermal tests, which are carried out in two ways. According to the first way, the temperature variation pattern over the rope cross-section is analyzed in subjecting the rope to thermal cycling by means of the contact method with the use of thermocouples and by means of remote measurements using an infrared imager. Recommendations regarding the procedure of carrying out rope temperature measurements under the production cycle field conditions are suggested. The second way implies studying the temperature variation pattern over the rope cross section in subjecting it to a short-term heating, which simulates the burst of flame from the ladle in pouring cast iron into the converter. It has been determined that the temperatures of rope core wires and outer wires of external strands may differ from each other by as much as several hundred degrees. It has been shown that ropes having a denser structure are characterized by better heat transfer between the wires and, as a consequence, feature more uniform temperature distribution over the rope cross-section. An experimental time dependence of the temperature gradient was used for estimating the stresses in wires based on a two-component rod-type analysis scheme. The change in the working rope safety margin under thermal cycling conditions was determined taking into account experimental data on the effect of temperature on the steel strength parameters. It has been shown that the real safety margin of a hot rope is essentially lower than its certified value in the rope delivery state. Possible rope failure cases are analyzed, and the hot rope strength criteria are formulated. A procedure for determining the two-parametric region of the permissible rope operating states on the basis of combined numerical and experimental assessments has been proposed. The suggested procedure makes it possible to determine in advance whether or not safe operation of the rope is possible given the existing technology of pouring cast iron into the converter. A general concept of unsafe operating conditions of hot metal crane ropes is given.

Research on wire rope stress distribution of WR-CVT

A wire rope continuously variable transmissions (WR-CVT) has been introduced in the paper, in view of its less research, this paper mainly studied the stress distribution of 6×7+IWS bending wire rope. The results shown that the wire stress is layered distribution in each section, the stress at the outer strand center wire and outer strand side wire was the greatest, the stress value of the outer strand side wire and metal block circular notch is second. As the transmission ratio decreases, the wire stress decreases, which is related to the pulley working radius increases. Compared with the section A1, the stress value on the section A2 is smaller, mainly because the section A2 is not in contact with the metal block or the contact pressure is small. This study provides a basis for the study of fatigue and wears failure of WR-CVT components.

Elastic-plastic modeling of metallic strands and wire ropes under axial tension and torsion loads

Elastic-plastic response is greatly involved in the failure of wire ropes. Based on the derivation of the local deformation parameters of individual wire, an analytical model characterizing the elastic-plastic behavior for both wire strands and multi-strand ropes is developed in this paper. Also, the contact status within a multilayered strand is carefully studied to achieve a full understanding of wire stresses. Details of the surface strain fields of ropes are captured by 3D digital image correlation (3D-DIC) technique and the results agree well with the prediction of the present model. Varying loading conditions are considered to analyze the yielding and failure behavior of wire strands. It is found that the rotation of ropes (no matter its positive or negative) will increase the overall stress level over the wire cross section, however, restraining the rope ends leads to higher contact stress. Increasing the helix angle moderately may be an effective method to reduce the contact pressure of strand wires. Our model provides straightforward prediction of the elastic-plastic response of wire ropes and proves an effective tool for rope design due to a great reduction of time consuming in numerical simulations.

An innovative approach for numerical simulation of stress relaxation of structural cables

Relaxation test on cable with large diameter is usually difficult and money consuming due to its extremely large ultimate tensile strength. A simplified finite element modeling method for stress relaxation simulation of steel wire, semi-parallel wire strands and spiral strands was proposed. Simplified relationship between stress relaxation and creep of steel wires was derived and a simplified modeling method on spiral wire composition was proposed. The whole numerical approach incorporated the steel wire creep model and the simplified cable compositions to realize the simulation of stress relaxation behavior of structural cables. The effectiveness of proposed creep calibration and cable stress relaxation simulations were verified through relaxation test data of single-wires and 19-wire semi-parallel wire strands. The 19-wire, 37-wire, 61-wire, 91-wire and 127-wire semi-parallel wire strands and spiral strands at different initial stress levels were all simulated. Due to the spiral wire composition and corresponding gradient wire stress distribution under axial tension, relaxation rate of semi-parallel wire strands and spiral strands were all larger than that of single steel wire. Semi-parallel wire strands presented a decreasing relaxation rate with the increase of cable dimension. Spiral strands had larger relaxation rate than similar-sized semi-parallel wire strands, and present a slight relaxation increase trend with cable dimension. The proposed finite element modeling method can realize the stress relaxation analysis of large diameter structural cables, with only stress relaxation test data of single wires or small diameter cables.

Analysis on the design of steel wire wound extrusion containers for hot extrusion process

Extrusion container is the most important tooling for steel hot extrusion process. Conventional design using large castings and forgings is very difficult to execute due to high cost and risk. Steel wire wound containers have many advantages over conventional designs. However, conventional wire wound containers are developed for use at room temperature which are not applicable to steel hot extrusion process. In this article, the impacts of preheating on the design of steel wire wound containers are discussed in detail. A finite element model was established to examine the preheating temperature distribution, and a 1:10 scaled extrusion container was manufactured to verify the effectiveness of the finite element model. Based on the finite element model–computed temperature field, thermal stress analysis was performed. The thermal impacts on the stress of extrusion container and steel wire were obtained. Results showed that insufficient stability of internal cylinder and greatly enhanced steel wire stress may lead to the failure of extrusion container. To solve the problems, an improved design was put forward by increasing the stability factor of internal cylinder, reducing the prestress factor and lowering the allowable stress of steel wire. Results showed that the improved design can meet the requirements and counteract the thermal impacts.

Research on modeling and bending stress distribution of a new metal belt continuously variable transmission

A wire-rope continuously variable transmission (WR-CVT) obtained by modifying a metal-belt continuously variable transmission (MB-CVT) is proposed. From a comparative analysis of the WR-CVT metal ring and the MB-CVT closed wire rope, the WR-CVT is found in preliminary findings to operate normally. Experiments on a WR-CVT prototype demonstrate the transmission principle confirming the finding. A geometric model of the closed wire rope with its distinctive strand pattern was developed using Pro/Engineer software. Using the finite element method, wire stress was analyzed with the results indicating that stress is less in the core strand than in the six outer strands. Each of the six outer strands has a side wire in contact with the semi-circular notch of the metal block. Stress is significantly higher in these two side wires than in the other side wires. The stress distribution in the WR-CVT closed wire rope is different from that of a wire rope in continuous sheave contact, indicating that the former with its discrete contact points with the metal blocks exhibits "stress stepping" different from that reported in previous studies.

수치해석을 이용한 탄소강 다단 신선 와이어 표면 잔류응력 예측

수치해석을 이용한 탄소강 다단 신선 와이어 표면 잔류응력 예측

109 The prognostic value of stress cmr in a tertiary centre

BackgroundStress cardiac magnetic resonance imaging (CMR) is increasingly being used in the assessment of myocardial perfusion at rest and in response to exertion. It provides information on the presence or...

Fatigue Damage Study of Helical Wires in Catenary Unbonded Flexible Riser Near Touchdown Point

This study presents an analytical model of flexible riser and implements it into finite-element software abaqus to investigate the fatigue damage of helical wires near touchdown point (TDP). In the analytical model, the interlayer contact pressure is simulated by setting up springs between adjacent interlayers. The spring stiffness is iteratively updated based on the interlayer penetration and separation conditions in the axisymmetric analysis. During the bending behavior, the axial stress of helical wire along the circumferential direction is traced to determine whether the axial force overcomes the interlayer friction force and thus lead to sliding. Based on the experimental data in the literature, the model is verified. The present study implements this model into abaqus to carry out the global analysis of the catenary flexible riser. In the global analysis, the riser–seabed interaction is simulated by using a hysteretic seabed model in the literature. The effect of the seabed stiffness and interlayer friction on the fatigue damage of helical wire near touchdown point is parametrically studied, and the results indicate that these two aspects significantly affect the helical wire fatigue damage, and the sliding of helical wires should be taken into account in the global analysis for accurate prediction of fatigue damage. Meanwhile, different from the steel catenary riser, high seabed stiffness may not correspond to high fatigue damage of helical wires.

Influence of Thermal Boundary Effects on the Process of Creating Recovery Stresses in a SMA Wire Activated by Joule Heating

The study deals with the influence of thermal boundary effects on the process of creating recovery stresses in a SMA wire activated by Joule heating, during a thermal cycle (up to the return to ambient temperature). First, a thermal characterization is performed using infrared thermography for temperature profile measurements along the wire in a steady-state regime. Second, recovery stress tests are performed using a uniaxial testing machine. Finally, tests are analyzed using a thermomechanical model, taking the inhomogeneous temperature distribution along the wire into account. The influence of the initial distribution of martensite (before thermal activation of the memory effect) is discussed, as well as the influence of the wire length. It is shown that the thermal boundary effects at the contact with the grips of the testing machine significantly influence the response of the wire. For instance, during the heating of the wire, an austenite-to-martensite transformation may occur in the zones near the wire ends (where the temperature remains close to ambient) due to the increased stress. A length of influence of the thermal boundary effects on the overall wire response is defined, and a condition to neglect this influence is proposed. The study highlights the importance of taking thermal boundary effects into account for practical applications of SMAs based on Joule heating.

Research on the Weathering Ability of NITI Shape Memory Alloys

In engineering practice, shape memory alloys need to keep stable basic properties such as memory effect and super elasticity in a different climate environment. In order to get the weather resistance of SMA, this article uses the high/low temperature test chamber to simulate different climate environments. The same parameters and the same batch of the SMA wires are taken as experimental objects. SMA wires static stretching experiments are performed after environmental box test. The experimental research shows, the SMA materials do not loss the basic mechanical properties for the environmental changes. The SMA wire stress changes can be neglected. The more cycles it takes, the larger residual strain it remains. After more than 120 cycles, the residual strain becomes stable and the SMA wires show good weathering ability.

Helical wire stress analysis of unbonded flexible riser under irregular response

A helical wire is a critical component of an unbonded flexible riser prone to fatigue failure. The helical wire has been the focus of much research work in recent years because of the complex multilayer construction of the flexible riser. The present study establishes an analytical model for the axisymmetric and bending analyses of an unbonded flexible riser. The interlayer contact under axisymmetric loads in this model is modeled by setting radial dummy springs between adjacent layers. The contact pressure is constant during the bending response and applied to determine the slipping friction force per unit helical wire. The model tracks the axial stress around the angular position at each time step to calculate the axial force gradient, then compares the axial force gradient with the slipping friction force to judge the helical wire slipping region, which would be applied to determine the bending stiffness for the next time step. The proposed model is verified against the experimental data in the literature. The bending moment–curvature relationship under irregular response is also qualitatively discussed. The stress at the critical point of the helical wire is investigated based on the model by considering the local flexure. The results indicate that the present model can well simulate the bending stiffness variation during irregular response, which has significant effect on the stress of helical wire.

Numerical Investigation of the Macroscopic Mechanical Behavior of NiTi-Hybrid Composites Subjected to Static Load–Unload–Reload Path

Shape memory alloys (SMAs) are a type of shape memory materials that recover large deformation and return to their primary shape by rising temperature. In the current research, the effect of embedding SMA wires on the macroscopic mechanical behavior of glass–epoxy composites is investigated through finite element simulations. A perfect interface between SMA wires and the host composite is assumed. Effects of various parameters such as SMA wires volume fraction, SMA wires pre-strain and temperature are investigated during loading–unloading and reloading steps by employing ANSYS software. In order to quantify the extent of induced compressive stress in the host composite and residual tensile stress in the SMA wires, a theoretical approach is presented. Finally, it was shown that smart structures fabricated using composite layers and pre-strained SMA wires exhibited overall stiffness reduction at both ambient and elevated temperatures which were increased by adding SMA volume fraction. Also, the induced compressive stress on the host composite was increased remarkably using 4% pre-strained SMA wires at elevated temperature. Results obtained by FE simulations were in good correlation with the rule of mixture predictions and available experimental data in the literature.

The Role of Overloading on the Reduction of Residual Stress by Cyclic Loading in Cold-Drawn Prestressing Steel Wires

Prestressing steel wires are commonly used as reinforcement elements in structures bearing fatigue loads. These wires are obtained by a conforming process called cold drawing, where a progressive reduction of the wire diameter is produced, causing residual stress in the commercial wire. The aim of this paper is to analyze the effect of diverse in-service cyclic loading conditions (cyclic loading and cyclic loading with overload) on such a residual stress field. To achieve this goal, firstly, a numerical simulation of the wire drawing process of a commercial prestressing steel wire was carried out to reveal the residual stress state induced by the manufacture technique. Afterwards, a numerical simulation was performed of the in-service loading conditions of a prestressing steel wire in which the previously calculated residual stress state is included. The analysis of the obtained results shows a significant reduction of the residual stress state of about 50% for common in-service loadings and as high as 90% for certain cases undergoing overloads during cyclic loading. Therefore, an improvement of the mechanical performance of these structural components during their life in-service can be achieved.

Research on Monitoring Force of Steel Wire Rope of Grab Dredger Base on Wireless Sensing

The article research on intelligent grab dredger. Work force mechanical model of steel wire is established during dredging Grab's flat digging working. Then, the theoretical calculation on stress of the steel wire is available. It's easy to get the result of dredging Grab's steel wire. Meanwhile, a way is put forward about changing the rotating shaft torque to the force of steel wire, which is based on detection of wireless sensor network technology in grab dredger's hoist. The ideal result on Real-time display of the curves of closing hoist and hoist rope's stress. The test result of real-time monitoring show that the theoretical calculation on stress of the steel wire is consistent with the test result of real-time monitoring, which provide the basis on the application of real-time monitoring of wireless sensor technology in the grab dredger's steel wire's stress.